A stationary large energy-storage system (ESS: Energy Storage System) can be used for electric power quality improvement such as for stabilization of electric power in power grids or local grids of factories, buildings or the like and reduction of frequency variations. Moreover, it is provided with a charge/discharge function to discharge electric power upon peak uses of consumers and charge with excessive electric power. Such an energy storage system is expected to expand a market in the future.
Before starting operation, an energy-storage system is subjected to performance tests to test whether predetermined performance is satisfied. In the performance test, charge/discharge command values assuming an actual operational environment are given. Generally, as the charge/discharge command values given in the test, simulation signals of existing data, constant currents, or combinations of sine waves, rectangular waves, triangle waves, etc. are used; wherein the values that reflect the actual operational environment as much as possible are desired. The characteristics, life, safety, etc. of batteries largely depend on the operational environment. Therefore, if reflection of the actual operational environment is not sufficient, the effects of customizing and safety measures based on test results become poor. Moreover, by obtaining precise test results, the replacement timing of batteries, etc. can be predicted with high precision, and countermeasure plans can be estimated in advance.
The charge/discharge command values in actual operation are superposition of charge/discharge commands of various uses of the energy-storage system. Therefore, the actual charge/discharge command values depend on various environmental factors of a grid to which the energy-storage system is connected and becomes extremely complex. Therefore, in operational tests, it has been difficult to generate charge/discharge command values which are extremely similar to those in the operational environment.